It is often postulated that 100% pure fruit juices induce a transient unfavourable increase blood sugar which may contribute to the development of type 2 diabetes. Yet, fruit juices generally are known to have a low glycemic index compared with sugar-sweetened beverages containing similar amounts of sugar (1). How can this be explained?

A series of new studies, published ahead of press in the British Journal of Nutrition (4), has investigated this question, finding that hesperidin – a polyphenol found in citrus fruits and juices – has the capacity to slow down glucose absorption in the gut.

The study combined in vitro assays with cross-over interventions in healthy volunteers. Using 14C-labelled glucose, the assays investigated how hesperidin influenced the body’s mechanisms for transporting glucose and fructose from the gut to the blood. Hesperidin was found to act on both GLUT2 and GLUT5 sugar transporters with the result of significantly reducing the rate of glucose uptake.

The concept was then tested in human volunteers over three randomised intervention trials using 1) 100% orange juice, 2) diluted orange juice (to mimic normal dilution in the stomach) and 3) a control drink with added sugars and vitamin C, quantitatively equivalent to their presence in 100% juice. Postprandial blood glucose levels were lower after the two test orange juices and this was most pronounced when the juice was diluted.

The researchers state that hesperidin did not impact on the digestive enzymes sucrase and amylase, which led to conclude that: “hesperidin or other non-nutrient components of orange juice could be acting to slow down the glucose absorption step through partial inhibition of intestinal sugar transport, which would lead to lowered maximum glucose blood glucose concentration, but result in no change in the total sugar absorbed, since the absorption can occur along the length of the intestine and would therefore be shifted to a later time”.

Taken in context with meta-analyses on metabolic health (2,3), it has been shown that consumption of 100% orange juice results in a reduced rate of glucose absorption by the action of hesperidin. This effect may explain the positive health effects of regular moderate orange juice consumption on cardiovascular and diabetes risk, compared with sugar sweetened beverages that raise these risks.

Kerimi A et al. (2019) Effect of the flavonoid hesperidin on glucose and fructose transport, sucrase activity and glycaemic response to orange juice in a cross-over trial on healthy volunteers. British Journal of Nutrition in press.

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